Winmail.dat

This is not an iPhone issue.

Sometimes when people send emails from an older version of Outlook on their computer, the attachment might show up as a strange 'Winmail.dat' file instead of the expected PDF. Here's how to fix it so you can see the PDF on your iPhone:

Ask the person who sent the email to change a setting in Outlook:

• Have them open your email address in their Outlook contacts.
• Double-click your email address to open its properties.
• Look for an option like 'Use TNEF (Rich Text) if sending to this contact by default'.
• Uncheck this option and select 'Let Outlook decide the best sending format'.
• Click OK.

You can open these files without having to go back to the sender. Download the free TNEF's Enough from the App Store.

https://www.joshjacob.com/mac-development/tnef.php

You may get better and prompt responses if you may kindly provide the iPhone Model that you have and the iOS version if it is known to you and re-post.

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